A single-sample synthesis concept based on multi-element ceramic samples can
produce a variety of local products. When applied to cuprate superconductors
(SC), statistical modelling predicts the occurrence of possible compounds in a
concentration range of about 50 ppm. In samples with such low concentrations,
determining which compositions are superconducting is a challenging task and
requires local probes or separation techniques. Here, we report results from
samples with seven components: BaO2, CaCO3, SrCO3, La2O3, PbCO3, ZrO2 and CuO
oxides and carbonates, starting from different grain sizes. The reacted
ceramics show different phases, particular grain growth, as well as variations
in homogeneity and superconducting properties. High-Tc superconductivity up to
118 K was found. Powder x-ray diffraction (XRD) in combination with
energy-dispersive spectroscopy (EDS), scanning transmission electron microscopy
(STEM) can assign Pb1223 and (Sr,Ca,Ba)0.7-1.0CuO2 phases in inhomogeneous
samples milled with 10 mm ball sizes. Rather uniform samples featuring strong
grain growth were obtained with 3 mm ball sizes, resulting in Tc =70 K
superconductivity of the La(Ba,Ca)2Cu3Ox based phase. Scanning SQUID microscopy
(SSM) establishes locally formed superconducting areas at a level of a few
microns in inhomogeneous superconducting particles captured by a magnetic
separation technique. The present results demonstrate a new synthetic approach
for attaining high-Tc superconductivity in compounds without Bi, Tl, Hg, or the
need for high-pressure synthesis